Infrared photodissociation spectra of the ionic complexes CH3+ -Ar-n (n = 1-8) have been recorded in the vicinity of the nu(3) asymmetric stretching vibration of the CH: monomer. The CH3+-Ar dimer has also been investigated in the spectral range of the first CH stretching overtones, resulting in the characterization of its 2 nu(1), nu(1) + nu(3), and 2 nu(3) vibrational states at the level of rotational resolution. The spectrum of CH3+-Ar is consistent with a pyramidal C-3 upsilon minimum structure of the complex predicted by ab initio calculations at the MP2 level, whereby the Ar atom is attached to the empty 2p(z) orbital of the CH3+ moiety. The rotationally resolved nu(3) spectrum of the CH3+-Ar-2 trimer indicates that the two Ar atoms are located on opposite sides of the CH3+ moiety on the C-3 axis, with significantly differing intermolecular C-Ar bond lengths. The splittings observed in the trimer spectrum are attributed to a tunneling motion between two equivalent C3u minimum configurations via a symmetric D-3h transition state. The spectra of larger clusters (n greater than or equal to 3) lack rotational resolution, however the positions and profiles of the nu(3) band suggest that the additional Ar atoms are weakly attached to CH3+-Ar-2 trimer, which acts as the effective nucleation center for the cluster growth. The stretching fundamentals of the CH3+ ion core in the CH3+-Ar-n clusters are intermediate between those of the methyl radical and the methyl cation, implying a substantial charge transfer from the rare gas atoms to the unoccupied 2pz orbital of CH3+ .